Operator&#39;s telephone-circuit.



O. E. BENSON.

OPERATORS TELEPHONE CIRCUIT.

APPLICATION FILED NOV. 21. 916.

Patented July 10, 1917.

@TdlTblD @TATE% PATENT OSCAR E. BENSON, 0F GLEN RIDGE, NEW JERSEY, ASSIGi-NOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

OPERATORS TELEPHONE-CIRCUIT.

Specification of Letters Patent.

Patented July 10, 11917.

Application filed November 21, 1916. Serial No. 132,545.

To all whom it may concern:

Be it known that I, OsoAR E. BENsoN, a citizen of the United States, residing at Glen Ridge, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Operators Telephone-Circuits, of which the following is a full, clear, concise, and exact description.

This invention relates to operators telephone circuits, and more lparticularly to such circuits for use with universal cord circuits.

The object of this invention is the production of a highly eflicient balanced operators telephone circuit for such service in which a minimum amount of apparatus is required.

Another object of this invention is the production of a highly eflicient operators telephone circuit which may be employed in making busy tests without the use of any auxiliary apparatus in the cord circuit.

This invention is illustrated in the accompanying drawing, in which there is shown the central office end of a common battery line A and of a magneto line B, and the calling end of the universal cord circuit 0..

lVithin the dotted lines there is shown an operators telephone circuit D, embodying the features of the present invention. The cut-off relay associated with common battery line is of low resistance and that associated with the magneto line is of high re sistance. The sleeve relay 5 in the cord circuit C is marginal and does not operate when connected in series with the relay, which is of high resistance, of a magneto line, but does operate when connected in series with the cutoff relay, which is of low resistance, of the common battery line. When the cord circuit is connected with the magneto line, relay 6 is bridged across the talking strands of the cord circuit, and when energized by generator current from a hand generator at the station on the magneto line, it locks up through its right-hand winding to light lamp 7 to furnish a signal to the operator. When the cord is connected with the common battery line, relay 5 operates to furnish battery to the talking strands of the cord circuit C through a supervisory relay 8. The sleeve relay 5 and supervisory relay 8 thereof cooperate to control the supervisory lamp 7 'tions 28 and 29.

The operators telephone circuit D may be connected to the talking strands of the cord circuit C by the actuation of listening-key 9, this key being provided with a contact 10 in the locking circuit of relay 6.

The operators telephone circuit comprises an induction coil 20 having a primary winding 21, in circuit with which is a battery 22, an impedance coil 23 and a condenser 24, there being a transmitter 25 connected, as shown, so as to receive battery supply from battery 22 through impedance coil 23, and to be in the talking circuit which includes the primary 21 of the induction coil and the condenser 24. Upon the same core with the primary winding 21 is wound a secondary winding comprising four sections 26, 27, 28 and 29, all of which are connected in series aiding. The impedance of section 27 is of the same value as that of section 28, while the impedance of sections 26 and 27 in series is of the same value as that of sections 28 and 29 in series. A receiver 30 has one terminal connected to the junction point between sections 26 and 27 of the secondary winding, and the other terminal thereof connected to the junction point between secvVith the receiver connected as shown and described, the secondary winding of the induction coil 20 acts as an autotransformer for receiving incoming currents. The middle point of the secondary winding at the junction point between the sections 27 and 28 is grounded to balance both sides of the operators telephone circuit, thereby to eliminate inductive noises in the receiver from ringing current traversing adjacent leads in the switchboard. The outer terminal of section 29 of the secondary winding is connected to conductor 31 terminating at a normally open contact on listening key 9 and which may be known as the ring conductor. In ring conductor 31 there is included a condenser 32 which is for the purpose of preventing the operation of supervisory relay 8 when the operators telephone circuit is connected to the cord circuit which may be connected to a common battery line. The terminal of section 26 of the secondary winding is connected to a conductor 33 terminating at a normally open contact on listening key 9 and which. may be known the tip conductor, In the tip conductor 33 there is included a condenser 34: for the purpose of balancing the tip side of the operators circuit with respect to the ring side. A resistance coil 35 of high resistance is legged from the tip conductor 33 to ground in bridge of the condenser 34: to form a discharge path for condenser 34, as will hereinafter more clearly appear. Legged to ring conductor 31 of the operators telephone circuit is a resistance coil 36 having the same resistance as coil 35, which is in bridge of the condenser 32 and is for the purpose of balancing the ring side of the circuit with respect to the tip side. The resistance of each of these coils 35 and 36 is made high enoughto prevent the false operation of supervisory relay 8 if the operators telephone circuit D should be connected to the cord circuit while it is connected to a common battery line.

Assuming that either common battery line A or the magneto line B is busy, due to the presence of the plug of another cord circuit similar to C in one of the jacks, and assuming further that the listening key 9 has been actuated to connect the operators telephone circuit D with the cord circuit, the

operator, in making a busytest, will touch the tip of the plug to the sleeve of a jack associated with the busy line. .Battery will be connected to the sleeve of this busy jack through the sleeve strand of the cord circuit in another jack of the line whereupon, when the tip of cord circuit C is brought into contact with the sleeve of the jack, battery will flow from the sleeve through the tip strand of the cord circuit C, upper listening-key contact, conductor 33, condenser 34, secondary windings, sections 26 and 27 to ground, thereby charging the condenser 34:. Due to the autotransformer action of the secondary winding of the induction coil 20, there will be a flow of current through the receiver, thereby producing a click which will be heard by the operator. Upon the removal of the tip from the sleeve of the jack, the condenser 34: will discharge through resistance 35 and sections 27 and 26, whereupon a second click will be heard by the operator. -What is claimed is: v

1'. An operators telephone .circuit comprising an induction coil, a primary winding therefor, a transmitter and a source of current in circuit with the primary winding, a secondary winding for the induction coil grounded at its middle point, a receiver in operative relation to the secondary winding and symmetrical with respect to the grounded middle point thereof, conductors connected to the terminals of the secondary winding, a condenser in each conductor, and a non-inductive resistance connected in parallel with one condenser and the portion of the secondary winding connected thereto.

2. An operators telephone circuit comprising an induction coil, a primary Winding therefor, a transmitter and a source of current in circuit with the primary, a sec ondary winding for the induction coil grounded at its middle point, a receiver in operative relation to the secondary winding and symmetrical with respect to'the grounded middlepoint thereof, conductors connected to the terminals of the secondary, a condenser in each conductor, and a noninductive resistance connected in parallel with each condenser and the portion of the secondary winding connected thereto.

3. An operators telephone circuit comprising an induction coil, a primary winding therefor, a transmitter and a source of current in circuit with the primary winding, a secondary winding for the induction coil grounded at its middle point, a receiver con,- nected to the secondary winding in symmetrical relation to the. grounded middle point thereof,conductors connected to the terminals of the secondary winding, a condenser in each conductor, and a high noninductive resistance connected in parallel with one condenser and the portion of the secondary winding connected thereto.

4. An operators telephone circuit comprising a two-conductor circuit, a high noninductive resistance bridge for the circuit grounded at its middle point, a high impedance bridge including an induction coil secondary winding for the circuit grounded at its middle point, a condenser in the lastmentioned bridge, a receiver I in operative relation-to the secondary and symmetrical with respect to the grounded middle point thereof, a primary winding in inductive relation to the secondary winding,and a transmitter and source of current in circuit with the primary winding.

5. An operators telephone circuit comprising a two-conductor circuit, a high noninductive bridge for the circuit grounded at its middle point, a high impedance bridge including an induction coil secondary winding for the circuit grounded at its middle point, condensers in the last mentioned bridge, a receiver connected to the secondary winding in symmetrical relation to the grounded middle point thereof, a primary winding in inductive relation to' the secondary winding, and a transmitter and source of current in circuit with the primary winding. V

In witness whereof, I hereunto subscribe my name this 20th day of November, A. D. 1916.

' OSCAR BENSON.

copies or this patent may be obtained for five cents each, by aderessing the "commissioner otaratentsp Washington, I). 0. 

